This invention relates to a rotary disk storage (memory) unit and a head suspension used in the storage unit, and more particularly to a rotary disk storage unit of a small size capable of high-precision positioning, and also to a head suspension for such a storage unit.
In a rotary disk storage unit, a head suspension presses a pneumatic bearing slider against a rotary disk recording medium. More specifically, the head suspension comprises a load beam of a sufficiently high rigidity to press the pneumatic bearing slider (having a transducer mounted thereon) against the rotary disk recording medium under a predetermined load, and a gimbal spring of a sufficiently low rigidity to allow the pneumatic bearing slider to follow fluctuations of the rotary disk recording medium. When the rotary disk storage unit is in its inoperative or deactivated condition, the pneumatic bearing slider is held in contact with the rotary disk recording medium. When the rotary disk storage unit is operated or activated, the rotary disk recording medium is rotated, so that a flying force due to an air stream between the pneumatic bearing slider and the rotary disk recording medium is produced, and the pneumatic bearing slider flies stably at a position where the flying force is balanced with the pressing load. Electrical connection between electrodes of the transducer formed on the pneumatic bearing slider and a read/write circuit of the rotary disk storage unit is made through tube-covered conductors (wires), and these tube-covered conductors are arranged over the head suspension.
When the rotary disk storage unit becomes smaller in size, so that the spacing between the adjacent rotary disk recording media becomes smaller, the pneumatic bearing slider and the head suspension need to be reduced in size. In order to achieve a small-size design of the head suspension, a type of head suspension in which a load beam and a gimbal spring are formed integral with each other has been put into practical use. Also, the pneumatic bearing slider has become smaller in size year after year.
With the small-size design of the pneumatic bearing slider and the head suspension, the tube-covered conductors become large relative to the pneumatic bearing slider and the head suspension, and the rigidity of the tube-covered conductors may lower the ability of the pneumatic bearing slider to follow fluctuation of the rotary disk recording medium, and also the tube-covered conductors may be cut upon contact with the surface of the rotary disk recording medium.
In the field of rotary disk storage units and particularly magnetic disk units, in order to obtain an increased storage capacity, a magneto-resistive transducer (hereinafter referred to as "MR head") suited for high-density recording has been developed. Since the MR head is a read-only head, an inductive head of a conventional type for writing purposes must be mounted, together with the MR head, on a pneumatic bearing slider, and as a result four tube-covered conductors in all are required for read/write purposes. Therefore, the rigidity of the tube-covered conductors is greater as compared with the case where two tube-covered conductors are used as in a read/write inductive head, and the load due to such increased rigidity tends to adversely affect the ability of motion of the pneumatic bearing slider.
On the other hand, Japanese Patent Unexamined Publication No. 1-162212 discloses a method in which instead of using tube-covered conductors, there is used a flexible sheet containing a plurality of conductors. In this construction, a flexible sheet is bonded to a head suspension comprising a metal load beam and a gimbal spring, and electrodes of a transducer are electrically connected to a read/write circuit of a rotary disk storage unit by conductors contained in this flexible sheet. With this construction, although there is no fear of cutting of the conductors, it is difficult to achieve a small-size design of the head suspension. Also, there is a possibility that a load due to the rigidity of the flexible sheet adversely affects the ability of motion of the pneumatic bearing slider at that portion where the flexible sheet is connected to the electrodes of the transducer formed on the pneumatic bearing slider.
Japanese Patent Unexamined Publication No. 3-71477 discloses a method in which a flexible sheet, having an electrical circuit formed thereon, is used instead of a head suspension, which drives the negative-pressure air bearing slider. In this construction, there is no fear of cutting of conductors, and the head suspension can be of a small size. However, the negative-pressure air bearing slider is supported by the flexible sheet in a cantilevered condition, and therefore when the negative-pressure air bearing slider is driven radially of a rotary disk recording medium by the actuator means, it is difficult to position the negative-pressure air bearing slider over the rotary disk recording medium precisely because of the low rigidity of the flexible sheet in the radial direction.